1. Field of the Invention
The present invention relates to a sound volume control device and a sound volume control method for collecting and amplifying an acoustic signal such as a hearing aid and a sound collector.
2. Description of the Related Art
For a hearing-impaired person, not only it is difficult to hear small sound but also a comfortably-acceptable sound level is limited. Moreover, there is a case in which, after the sound has reached an audible level, the sound is felt to be annoying comparatively soon as the sound volume is further increased. It has been known that hearing impairment showing such a recruitment phenomenon exists. Accordingly, in an device which inputs sound simply collected by a microphone into an amplifier and increases sound volume to an audible level by increasing volume of the amplifier to provide the amplified sound for hearing using an earphone, there arises a problem depending on the kind of hearing impairment that the sound volume becomes excessive when the sound volume has changed in a sound source.
Therefore, an auditory supplement device for a hearing-impaired person such as a hearing aid needs to have amplification characteristics set to fit an individual's auditory property, and this is one of reasons why adjustment is difficult and requires fitting by a specialist or the like.
Accordingly, there have been proposed conventionally an acoustic characteristic checking device (refer to Patent document 1 “Japanese Patent Application Laid-Open Publication No. S62-125800”, for example) such as an order-made type hearing aid in which the acoustic characteristics of the order-made type hearing aid are fitted with the auditory property of a hearing-impaired person when the hearing-impaired person purchases the order-made type hearing aid, and a hearing aid adjustment device or a hearing aid (refer to Patent document 2 “Japanese Patent Application Laid-Open Publication No. 2001-204098, for example) which is configured to provide a sound quality suitable for an individual user thereof by asking the subject to hear audibility data in a range from a minimum audible value to an uncomfortable threshold value.
However, since each of the sound volume control devices of Patent documents 1 and 2 is configured to ask the user to actually hear test audibility data, there is a problem that burden on a user of the subject is heavy.
Further, the subject feels difference between component ratios of frequency components included in the audibility data used for the measurement and those included in sound felt to be annoying in actual life. Accordingly, there is also a problem that, only by the measurement using test equipment which provides limited test sound, it is difficult to specify acceptable maximum sound volume for each frequency band and it cannot be expected to obtain a good result.
Further, when the excessive sound volume is avoided by means of compressing a dynamic range across the whole frequency band, sometimes target sound is buried in noise and the sound becomes difficult to hear and poor in expression.